Renewable energy - why?

A source of income

Apart from benefiting the world’s environment and lowering climate change, the use of organic materials, especially waste materials, in the biogas process transforms the owner of the installation into an energy producer and generates for him a significant income. This is most apparent in Europe where in line with the European Unions‘s Directive of targeting the production of 20% of its energy from renewable sources by the year 2020, more and more countries in Europe are introducing favorable feed-in tariffs for energy produced from biogas (see following chart). In Germany, for example, at the end of 2007 there were more than 4.000 operating biogas plants providing 1,270 MW/h of electricity, and the energy produced from biogas is expected to reach 3,000 MW/h by the year 2020. Countries outside of Europe are also joining the trend, and President Obama has legislated recently an incentive package for the biogas industry in the USA. A recent UN study has indicated that more than 100.000 biogas plants will be build world-wide until 2025.

In the wake of these legislative changes numerous renewable energy funds have sprung up all over the world in order to enable investors to enter this lucrative market. The renewable energy industry has suffered the least during the recent economic recession, and is seen as one of the most promising growth sectors of the world’s economy.

The Greenhouse Effect

The world currently experiences the adverse effects of the Greenhouse Effect. The climate is changing, violent weather changes and atmospheric turbulences, which did not occur in the past, take place.

This is the result of increased emission into the atmosphere of carbon dioxide (CO2) from the burning of fossil fuels – oil, gas and coal, as well as methane (CH4) produced from animal excrements. One unit for methane is 21 times more damaging to the atmosphere than a unit of CO2 is. Biogas installations considerably reduce methane emission and substitute fossil fuels.

Increase in energy prices

Over the past 50 years energy prices have considerably and constantly increased due to the depletion of fossil fuel reserves and the increased costs of developing new ones. Renewable energy is created from hitherto untapped sources, and consequently reduces energy prices.

Energy independance

The majority of fossil fuels are produced in politically unstable regions of the world, so the reliance on these sources subjects the consumers to uncertainty of supply as well as to violently fluctuating prices.

Environmental protection

The traditional means for the disposal of waste in landfills and similar solutions have created an ecological nuisance such as pungent smells and bacteriological hazard. The utilization of these wastes in the biogas process eliminates these hazards.

Government incentives and subsidies

For all the above reasons, the necessity to increase the production of renewable energy has been upheld by the majority of governments in the world. Most European countries, the USA and other countries have recently been instituting a variety of favourable feed-in electricity tariffs, as well as other grants, tax benefits and subsidies intended to encourage the production of renewable energy. The energy produced from biogas is a major source of renewable electricity and heat, alongside with energy produced from wind, solar, hydro-electric and geothermal sources.

What is a biogas plant?

What is biogas?

Biogas is a gas whose primary elements are about 65% of methane (CH4) and about 35% of carbon dioxide (CO2). It is a product of the natural decomposition of any organic substance of animal or plant origin due to the activity of anaerobic (functioning in a non-oxygen environment) bacteria. Major sources of methane are all animal excrements, waste landfills, and any other organic material which is left untreated.

The bacteria involved in the process are methanogenic bacteria, which are subdivided into psychrophilic, mesophilic and thermophilic strains according to their optimum temperature range. The optimum temperature for mesophilic bacteria lies in the range 30°C – 35°C, while the thermophilic group prefers 50°C – 60°C. The pH value of the fermentation substrate lies between weakly acidic (ca. pH 6) and weakly alkaline (ca. pH 8). Antibiotics, disinfectants and other chemicals present in the substrate can seriously inhibit or even stop completely the fermentation process.

The main product from this fermentation is biogas, an energy source for the generation of renewable energy. The components of biogas – methane and carbon dioxide - act as greenhouse gases that harm the environment if released unburned into the atmosphere. The production of biogas in biogas plants prevents uncontrolled emission of methane into the atmosphere and, by generating renewable energy in the form of biogas, reduces the use of fossil fuel.

What is a biogas plant?

Substrates in the form of organic material such as animal excrements, remnants of food processing, silage from plants, slaughterhouse leftovers and almost any other organic material are ground and fed into large (2.500 to 5.000 cubic metres) hermetically-closed containers known as digesters. In the digesters these substrates are heated to an optimal temperature and agitated so as to produce biogas, which bubbles to the top of the substrate and is collected in a biogas container. This biogas is fed into an electric generator which produces electricity and heat. The whole process is electronically monitored.The remaining substrate can be used as a high quality ecological fertilizer.

Technology and Process

Biogas plants installed by Biogas Nord use a digester through-flow procedure, which involves the operation of one or more digester through which substrate is continuously fed. The digester and storage containers built by the company are stationary, cylindrical containers made of reinforced concrete. Their size, quantity and equipment depend on the type and quantity of the input substances being treated.

Powerful pumps or apparatus for loading solids such as conveying screws or sliding floors are used to load the raw materials. Substrates for co-fermentation plants must be hygenised – heated to a pre-defined temperature – before being loaded into the digesters. The digesters are fitted with up to four stirring devices and double membrane roofs for the purposes of gas storage. The double membrane comprises an inner film for holding the gas, and an outer film to protect against the weather. Wall and floor heaters are installed inside the concrete walls of the digester. The exterior walls of the digesters are thermally-insulated, and are also lined with trapezoid bodywork.

After cleaning the hydrogen sulphide content from the biogas it is converted into electrical and thermal energy in an electric generator. Part of the electrical energy produced is used for the energy needs of the biogas plant itself, the rest is fed into the public electricity network. Part of the generated thermal energy is utilised for heating the digesters, while the excess heat can be used to heat residential homes and buildings, as well as in agricultural or industrial processes with high thermal energy requirements.

Planning

Based on a detailed questionnaire, Biogas Nord draws up the optimal design for the plant, including a comprehensive profitability analysis tailored to the specific plant. This gives the site owner a breakdown of the required investment, the expected biogas and energy production and the expected profitability of the biogas plant. Then implementation plans for the construction of the plant on the premises are drawn, and the necessary approval documents which provide support for public funding applications are compiled.

Permitting

We draw up the implementation plans for the construction of the plant on your premises, compile the necessary approval documents and provide support for public funding applications. In this way Biogas Nord relieves you of the responsibility for drawing up the documents permitting the construction and other legal and administrative procedures, and administers the approval process right up until the granting of approval.

Construction

Biogas Nord’s team of qualified and experienced personnel made up of engineers, biologists, business management specialists and technicians accompanies you every step of the way, from the planning phase to construction, down to the commissioning of the biogas plant.

Biogas Nord assumes responsibility for the full implementation of the entire construction scheme with its own project and construction managers and competent and experienced assembly teams.

Start up

Once the building of the plant is completed, the plant undergoes the start-up phase. The optimal substrate composition is found. Then bacterial flora is developed with injected serum slurry, the fermenter is heated externally, and the feeding quantities and times are adjusted.